Edge-damped diaphragm for electrodynamic loudspeakers

ABSTRACT

A diaphragm having a damping member formed of soft rubber compressed and retained at its outer periphery by a crimped flange to damp undesirable vibrations in the diaphragm.

Unlted States Patent 11 1 1111 3,837,425 Bozak Se t. 24, 1974 [54] EDGE-DAMPED DIAPHRAGM FOR 1.554.794 9/1925 De Forest 181/32 R ELECTRODYNAMIC LOUDSPEAKERS 1,783,385 12/1930 Nystrom 181/32 R 7 2,815,823 12/1957 7 Olson 61 al.. 181/32 R Inventor: Rudolph Bozak, Darien, Conn 3,019,849 2/1962 King 181/32 R [73] Assignee: Bozak, Inc., Darien, Conn. V

F1 2 1 1 7 Primary Examiner-Stephen J. Tomsky A N 12:9 77 9 3 Attorney, Agent, or FirmEyre, Mann & Lucas 52 U.S.C1 1111 3 21; 1 R C [51] Int. Cl G10k 13/00, H04r 7/00 A di D aphragm havmg a dampmg member formed of [58] Fleld of Search 181/32 32 179/181 R soft rubber compressed and retained at its outer periphery by.a crimped flange to damp undesirable vi- [561 References cued brations in the diaphragm. 4

UNITED STATES PATENTS 1 1,523,670 7 1/ 1925 5 Claims, 2 Drawing Figures Sutline 181/32 R EDGE-DAMPED DIAPHRAGM FOR ELECTRODYNAMIC LOUDSPEAKERS BACKGROUND OF THE INVENTION The R. T. Bozak Mfg. Company, and the disclosure of 1 this patent is incorporated herein by reference.

The problem of eliminating undesirable vibrations in loudspeaker diaphragms arises from the inherent lack of rigidity of these necessarily lightweight components of dynamic loudspeakers. Various means for rigidifying the diaphragm have been employed with limited success in an effort to eliminate these vibrations, which I FIG. 2 is a partial sectional side view of the diaphragm shown in FIG. 1, taken along line 2-2.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawing, the diaphragm l8 shown is preferably formed of any suitable lightweight have been known to cause a number of problems including resonance of the corrugated annulus (wale or surround) which connects the diaphragm to the loudspeaker housing. In an effort to overcome this problem, an annular soft foam rubber or sponge member has been employed at the outer edge of the diaphragm in the device shown in U.S. Pat. No. 2,815,823 (Olson). However, there remains the problem of reflection from the edge of the diaphragm of radially-propagated vibramaterial and is preferably coated with a damping material in accordance with the teaching of the referenced patent. The reference numerals shown in the drawing are the same for the same components or parts of components shown in the drawing of the referenced patent. In constructing the diaphragm embodying the'present invention, the flange 22 extending around the periph- 5 ery of diaphragm 18 is initailly upstanding as described in the referenced patent. The damping member 40 is of annular configuration and has an adhesive bottom side which is fixed to the upper surface of annular rim 42 and to at least a portion of the inner face of vertical step 44. Flange 22 is then crimped or bent radially inward to compress and further secure the damping member 40 in position at the edge of the diaphragm. The damping member 40 is preferably formed of low durometer (i.e., soft) rubber, but maybe of any other material which is capable of achieving the desired clamping of radially-propagated waves and resonance waves. The compliant annulus (wale or surround) for mounting the diaphragm, shown in phantom in FIG. 2,

' is affixed to the diaphragm by being glued to the annutions. Such vibrations result from the rigidity of the thin, lightweight diaphragm, which has the characteristic of low attenuation of such radial vibrations. If such vibrations are allowed to be reflected at the, diaphragms edge, they'will cause cancellation of particular frequencies, resulting in a valley or hole in the frequency response characteristic of the loudspeaker as well as increased harmonic distortion. Furthermore, metallic loudspeaker diaphragms also have a bell mode of vibration at some frequency withinthe operating range of the loudspeaker. This phenomenon is'basically a mechanical resonance inherent in the diaphragm, which results in a sharp peak in the frequency response 1 characteristic of the loudspeaker. This phenomenon is objectionable because it is perceived by the listener as a coloration or distortion of the sound being reproduced, and causes a piercing sensation in the ear of the listener. It is the purpose of the present invention to minimize these undesirable vibrations in lightweight aphragms, and thereby improve the frequency response characteristic of the loudspeakers of which the diaphragms form a part.

SUMMARY OF THE INVENTION The present invention is embodied inand carried out by a diaphragm having an annular member formed of soft rubber positioned at the outer periphery of the diaphragm and compressedly secured thereto by a crimped flange.

BRIEF DESCRIPTION OF THE DRAWING lar rim 42 of the diaphragm l8,'which rim underlies damping member 40 and in cooperation with crimped flange 22 applies compressive force to a substantial portion of clamping member 40. The combination of the soft rubber annulus thus positioned at the outer periphery of the diaphragm 18, and the crimping of the flange 22, yield superior results in terms of the reduction of undesirable vibrations in the diaphragm.

The advantages of the present invention, as well as certain changes and modifications of the disclosed embodiment thereof, will be readily apparent to those skilled in the art. It is the applicants intention to cover all those changes and modifications which could'be made to the embodiment of the invention herein chosen for the purposes of the disclosure without departing from the spirit and scopeof the invention.

What is claimed is: v

l. A loudspeaker diaphragm comprising a thin, lightweight sheet and a damping member retained and partially compressed at the outer periphery of said sheet by a crimped flange.

2. A loudspeakerdiaphragm according to claim 1 wherein said sheet has an annular rim, and at least a first portion of the bottom surface of said damping member is adhesively secured to the upper surface of said annular rim. I I

3. A loudspeaker diaphragmaccording to claim 2 wherein said sheet has a vertical step extending from the inner periphery of said annular rim, and a second portion of thebottom surface of said clamping member is adhesively secured to at least a portion of the inner.

5. A loudspeaker. diaphragm according to claim 1 I wherein said damping member 'is formed of soft rubber. 

1. A loudspeaker diaphragm comprising a thin, lightweight sheet and a damping member retained and partially compressed at the outer periphery of said sheet by a crimped flange.
 2. A loudspeaker diaphragm according to claim 1 wherein said sheet has an annular rim, and at least a first portion of the bottom surface of said damping member is adhesively secured to the upper surface of said annular rim.
 3. A loudspeaker diaphragm according to claim 2 wherein said sheet has a vertical step extending from the inner periphery of said annular rim, and a second portion of the bottom surface of said damping member is adhesively secured to at least a portion of the inner face of said vertical step.
 4. A loudspeaker diaphragm according to claim 1 wherein said damping member is of annular configuration.
 5. A loudspeaker diaphragm according to claim 1 wherein said damping member is formed of soft rubber. 